Carbohydrate Hydrolase-Inhibitory Activity of Juice-Based Phenolic Extracts in Correlation to Their Anthocyanin/Copigment Profile

Chromogenic Assay Is More Efficient in Identifying α-Amylase Inhibitory Properties of Anthocyanin-Rich Samples When Compared to the 3,5-Dinitrosalicylic Acid (DNS) Assay

The inhibition of carbohydrate digestion by plant bioactive compounds is a potential dietary strategy to counteract type 2 diabetes. Indeed, inhibition of α-amylase, a key enzyme that carries out the bulk of starch digestion, has been demonstrated for a range of bioactive compounds including anthocyanins; however, sample pigmentation often interferes with measurements, affecting colorimetric assay outcomes. Therefore, the present study compared the performance of a direct chromogenic assay, using 2-chloro-4 nitrophenyl α-D-maltotrioside (CNPG3) as a substrate, with the commonly used 3,5-dinitrosalicylic acid (DNS) assay. The direct chromogenic assay demonstrated a 5-10-fold higher sensitivity to determine α-amylase inhibition in various samples, including acarbose as a reference, pure anthocyanins, and anthocyanin-rich samples. The IC50 values of acarbose presented as 37.6 μg/mL and 3.72 μg/mL for the DNS assay and the direct chromogenic assay, respectively, whereas purified anthocyanins from blackcurrant showed IC50 values of 227.4 µg/mL and 35.0 µg/mL. The direct chromogenic assay is easy to perform, fast, reproducible, and suitable for high-throughput screening of pigmented α-amylase inhibitors.

LC-MS metabolomics profiling of Salvia aegyptiaca L. and S. lanigera Poir. with the antimicrobial properties of their extracts

BACKGROUND

Salvia L. (Lamiaceae) found in almost all countries in temperate and tropical regions. Both S. aegyptiaca L. and S. lanigera Poir. have a rather wide distribution in Egypt (Mediterranean region, Gebel Elba and nearly the whole Sinai). Salvia species showed antibacterial and antifungal activities against several groups of food microorganisms and pathogens, so they are considered as a natural foods preservatives.

AIM

Investigate the phytochemical profiles of S. aegyptiaca & S. lanigera collected from their natural habitats in Egypt and test the antimicrobial activities of both species against some bacteria and fungi pathogenic strains.

METHODOLOGY

In the present study, S. aegyptiaca and S. lanigera were collected from their natural habitat. Total phenolics and flavonoids contents were measured for aerial parts of both Salvia spp.. The separation and identification of the pure active materials of both Salvia sp. by using LC-MS system (UHPLC-TSQ Quantum Mass Spectrometer). The antimicrobial activities of the ethanol, water and benzene extracts of the two species were tested against different pathogenic strains and compared with the standard antimicrobial drug (Gentamycin). Antimicrobial activity was determined by using agar disk diffusion method.

RESULTS

The phenolics content in S. lanigera 132.61±6.23 mg/g and S. aegyptiaca 125.19±4.97 mg/g, while the flavonoids content was 35.68±1.84 and 40.63±2.11 mg/g, respectively. Through LC-MS analysis, two compounds were detected in both species; heptadecanoyl coenzyme A, that the highest percentage (13.5%) in S. aegyptiaca and (11.5 %) in S. lanigera. Oenin, in a peak area of 3.1% in S. aegyptiaca and 1.2 % in S. lanigera. Ethanol extract of the two species had the most inhibitory effect against all tested microorganisms that exceeded the effect of the standard, except for Mucor reinelloids which was more sensitive to the water extract. Moreover, S. lanigera ethanol extract showed larger inhibition zone than S. aegyptiaca in all tested microorganisms except for Pseudomonas aeruginosa.

CONCLUSION

This study shows the important phytochemicals that improve the antibacterial and antifungal activities of Salvia aegyptiaca and S. lanigera.

Production of High-Quality Red Fruit Juices by Athermal Membrane Processes

Membrane-based processes are increasingly used to clarify and concentrate thermo-sensitive fruit juices and plant extracts as alternatives to conventional processes. This work aimed to evaluate the quality of red fruit juices clarified and concentrated by an integrated membrane process with special regard to the preservation of valuable compounds. A red fruit juice obtained from a blend of pomegranate, cactus pear, and red orange juices of Sicilian origin was clarified by microfiltration (MF) and then pre-concentrated up to 33 °Brix by nanofiltration (NF). The pre-concentrated juice was finally concentrated by osmotic distillation (OD) up to 50 and 60 °Brix. Samples of clarified, pre-concentrated, and concentrated juice were analyzed for their physico-chemical composition and in terms of the antioxidant activity and inhibitory activity against α-amylase and lipase. The results clearly confirmed the assumption of a mild fruit juice processing method, allowing us to preserve the original nutritional and functional properties of the fresh juice. In particular, the OD retentate at 60 °Brix resulted the most active sample against pancreatic lipase and α-amylase inhibitory activity with IC50 values of 44.36 and 214.65 μg/mL, respectively.

Phytochemical Analysis, α-Glucosidase and α-Amylase Inhibitory Activities and Acute Toxicity Studies of Extracts from Pomegranate (Punica granatum) Bark, a Valuable Agro-Industrial By-Product

Punica granatum is a tree of the Punicaceae family which is widespread all over the world with several types of varieties. Its fruit juice is highly prized, whereas the bark, rich in in phytochemicals such as flavonoids, hydrolysable tannins, phenolic acids, and fatty acids, is regarded an agro-industrial waste. It is utilized in traditional medicine for its medicinal properties in the treatment and prevention of a variety of ailments. This study aims to extract and to separate the phytochemical compounds from the bark of P. granatum, to identify them and to study the inhibitory effect of its extracts against antidiabetic activity. First, we carried out successive hot extractions with solvents (chloroform, acetone, methanol, and water) of increasing polarity by the Soxhlet. Then, using both qualitative and quantitative phytochemical investigation, we were able to identify groups of chemicals that were present in all extracts. We identified the majority of the molecular structures of chemicals found in each extract using HPLC-DAD analysis. The inhibition against both intestinal α-glucosidase and pancreatic α-amylase enzymes by P. granatum extracts was used to evaluate their potential antidiabetic effect in vitro. Our results demonstrated the great potential of the acetone extract. Ellagic acid, (−)-catechin, vanillin and vanillic acid were proposed as the most active compounds by the correlation analysis, and their actions were confirmed through the calculation of their IC₅₀ and the determination of their inhibition mechanisms by molecular modelling. To summarize, these results showed that P. granatum bark, a natural agro-industrial by-product, may constitute a promising option for antidiabetic therapeutic therapy.

Influence of Brewer's Spent Grain Compounds on Glucose Metabolism Enzymes

With a yearly production of about 39 million tons, brewer’s spent grain (BSG) is the most abundant brewing industry byproduct. Because it is rich in fiber and protein, it is commonly used as cattle feed but could also be used within the human diet. Additionally, it contains many bioactive substances such as hydroxycinnamic acids that are known to be antioxidants and potent inhibitors of enzymes of glucose metabolism. Therefore, our study aim was to prepare different extracts—A1-A7 (solid-liquid extraction with 60% acetone); HE1-HE6 (alkaline hydrolysis followed by ethyl acetate extraction) and HA1-HA3 (60% acetone extraction of alkaline residue)—from various BSGs which were characterized for their total phenolic (TPC) and total flavonoid (TFC) contents, before conducting in vitro studies on their effects on the glucose metabolism enzymes α-amylase, α-glucosidase, dipeptidyl peptidase IV (DPP IV), and glycogen phosphorylase α (GPα). Depending on the extraction procedures, TPCs ranged from 20–350 µg gallic acid equivalents/mg extract and TFCs were as high as 94 µg catechin equivalents/mg extract. Strong inhibition of glucose metabolism enzymes was also observed: the IC₅₀ values for α-glucosidase inhibition ranged from 67.4 ± 8.1 µg/mL to 268.1 ± 29.4 µg/mL, for DPP IV inhibition they ranged from 290.6 ± 97.4 to 778.4 ± 95.5 µg/mL and for GPα enzyme inhibition from 12.6 ± 1.1 to 261 ± 6 µg/mL. However, the extracts did not strongly inhibit α-amylase. In general, the A extracts from solid-liquid extraction with 60% acetone showed stronger inhibitory potential towards a-glucosidase and GPα than other extracts whereby no correlation with TPC or TFC were observed. Additionally, DPP IV was mainly inhibited by HE extracts but the effect was not of biological relevance. Our results show that BSG is a potent source of α-glucosidase and GPα inhibitors, but further research is needed to identify these bioactive compounds within BSG extracts focusing on extracts from solid-liquid extraction with 60% acetone.

GC-MS Metabolic Profile and α-Glucosidase-, α-Amylase-, Lipase-, and Acetylcholinesterase-Inhibitory Activities of Eight Peach Varieties

The inhibition of certain digestive enzymes by target food matrices represents a new approach in the treatment of socially significant diseases. Proving the ability of fruits to inhibit such enzymes can support the inclusion of specific varieties in the daily diets of patients with diabetes, obesity, Alzheimer's disease, etc., providing them with much more than just valuable micro- and macromolecules. The current study aimed atidentifying and comparing the GC-MS metabolic profiles of eight peach varieties ("Filina", "Ufo 4, "Gergana", "Laskava", "July Lady", "Flat Queen", "Evmolpiya", and "Morsiani 90") grown in Bulgaria (local and introduced) and to evaluate the inhibitory potential of their extracts towards α-glucosidase, α-amylase, lipase, and acetylcholinesterase. In order to confirm samples' differences or similarities, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were also applied to the identified metabolites. The results provide important insights into the metabolomic profiles of the eight peach varieties and represent a first attempt to characterize the peels of the peach varieties with respect to α-glucosidase-, α-amylase-, lipase-, and acetylcholinesterase-inhibitory activities. All of the studied peach extracts displayed inhibitory activity towards α-glucosidase (IC₅₀: 125-757 mg/mL) and acetylcholinesterase (IC₅₀: 60-739 mg/mL), but none of them affected α-amylase activity. Five of the eight varieties showed inhibitory activity towards porcine pancreatic lipase (IC₅₀: 24-167 mg/mL). The obtained results validate the usefulness of peaches and nectarines as valuable sources of natural agents beneficial for human health, although further detailed investigation should be performed in order to thoroughly identify the enzyme inhibitors responsible for each activity.

Assessing the ethnobotanical potential of Carissa opaca berries by merging outcomes from metabolomics profiling, enzyme assays, and in silico docking studies

The phytochemical profile of Carissa opaca fruit extract and fractions was established through dereplication strategies employing LC-MS/MS and global natural product social molecular networking (GNPS). Crude extract and fractions were evaluated for their potential to inhibit α-glucosidase and urease in vitro. Flavonoid-O-glycosides, flavonoid-C-glycosides, flavonoids, proanthocyanidin B2, phenolics, and triterpenoids were annotated as the major classes of secondary metabolites present in the extract and fractions. α-Glucosidase inhibition was associated with n-butanol and ethyl acetate fractions comparable to acarbose (IC₅₀ = 120.43 µg/mL) with IC₅₀ values of 123.67 and 131.72 µg/mL, respectively. The ethyl acetate fraction showed good urease inhibition comparable with thiourea (IC₅₀ = 103.71 µg/mL) with an IC₅₀ value of 109.14 µg/mL. Molecular docking studies of compounds observed in the crude extract and bioactive fractions had significant binding scores, which supported results for enzyme inhibition in vitro. This study provided a detailed phytochemical profile of C. opaca fruit and its enzyme inhibition potential.